21. _______ influences the properties of GaAs field-effect transistor.
A. length dependency
B. structural dependency
C. material dependency
D. orientation dependency
Answer: D
Orientation dependency influences the properties of GaAs field-effect transistors. Factors like etching of the crystal, ion implantation, and passivation introduce the concept of orientation dependency.
22. The ion is steered ________ of the lattice.
A. up the open directions
B. down the open directions
C. up the closed directions
D. down the closed directions
Answer: B
When a high-energy ion enters a single crystal lattice, the ion is steered down the open directions of the lattice. This steering is called axial channelling.
23. If the equivalent direction is not used ______ will be increased.
A. ion concentration
B. steering angle
C. area coverage
D. depth distribution
Answer: D
If a random equivalent direction is not used during ion implantation, the depth distribution will be greater than those predicted by range statistics which are used to establish penetration depth.
24. Electrons become hot in gallium arsenide when the energy of
A. lower valley electrons decreases
B. lower valley electrons rises
C. higher valley electrons decreases
D. higher valley electrons rises
Answer: B
In gallium arsenide, when the energy of lower valley electrons rises sufficiently at a higher electric field, the electrons become hot.
25. When electrons become hot, drift velocity
A. increases
B. decreases
C. remains the same
D. does not depend on drift velocity
Answer: B
When electrons become hot, there will be a reduction in the number of high mobility electrons and hence a decrease in drift velocity.
26. ______ is a direct gap material with a valence bond maximum.
A. silicon
B. gallium oxide
C. gallium arsenide
D. silicon arsenide
Answer: C
Gallium arsenide is a direct gap material with a valence bond maximum and conduction band minimum.
27. Narrow valleys correspond to
A. electrons with lower mass state
B. protons with lower mass state
C. electrons with a higher mass state
D. protons with higher mass state
Answer: A
Valleys with band structures that are narrow and sharply curved correspond to electrons with a low effective mass state while valleys that are wide are characterized by larger effective masses.
28. The curvature of ___________ determines the effective mass of electrons.
A. energy versus concentration
B. energy versus mass
C. energy versus momentum
D. energy versus structural design
Answer: C
The curvature of the energy versus electron momentum profile determines the effective mass of electrons traveling through the crystal.
29. Conduction band minimum occurs at
A. low momentum
B. high momentum
C. all of the mentioned
D. none of the mentioned
Answer: B
The minimum point of gallium arsenide’s conduction band is near the zero point of the crystal-lattice momentum. Conduction band minimum occurs at high momentum.
30. Mobility depends on
A. concentration of impurity
B. temperature
C. electron efficient mass
D. all of the mentioned
Answer: D
Mobility depends on several factors such as concentration of impurity, and temperature and is relatively related to electron efficient mass.
